Lath for boat-sails



F. LJUNGSTRCM.

LATH FOR BOAT- SAILS.

APPLICATION FILED MAR.3. 1920.

1,3 2,950. Patented Dec. 21, 1920.

1. L un ailing dam-W UNITED STATES FREDRIK LJUNGsTnoM, or BREVIK, LIDINGGN, swnnnn.

LATH non BOAT-SAILS.

Specification of Letters Patent.

Patented Dec. 21, 1920.

Application filed March 3, 1920. Serial No. 363,057,

To all whom it may concern:

Be it known that I, FREDRIK LJUNesrRoM, chief engineer, subject of the King of Sweden, residing at Brevik, Lidingon, Sweden, have invented certain new and useful Improvements in Laths for Boat-Sails, of which the following is a specification.

In boat sails, laths have been used, in order partly to make the sail spread as evenly as possible, and partly to revent it from shivering in strong winds. eretofore, these laths have been straight and generally, as thin as possible in order to render them pliable enough not to counteract the tendency of the sail to form a bag. In strong winds and in careless handling of these laths they are apt to break. If in order to obviate this drawback, the laths are made somewhat thicker, the sail cannot assume the most suitable bulge.

The object of the present invention is to avoid these drawbacks, and to this end the lath is given a curved shape, and so inserted in the sail or attached'thereto that it may assume different angular positions relatively to a plane through the ends of the lath and the aft leech of the sail or the mast respectively. By this means the lath may in every instance, assume a position wherein its curvature corresponds to the natural bulge of the sail, and, when the sail is. slack, it may be in the plane of the sail Without causing any bulging whatever of the sail.

The curvature of the lath should be directed downwardly in the plane of the sail, and that part of the lath whose radius of curvature is the smallest should be located nearer to the mast than to the after leech.

The curvature of the lath is preferably such that the part of it extending on the one side of the vertex is somewhat longer than the part extending on the other side of the vertex. Preferably, both of the said parts are straight or nearly so, but, if desired, they may be curved in such a manner that the radius of the curvature, which is the smallest at the vertex of the lath, increases toward the ends thereof.

The lath may be of any Wanted length and may extend from the after leech of the sail or from the fore leech to any point between the after leech and the fore leech and, if wanted, it may extend right across the sail from the after leech to the fore leech.

The invention is ilustrated in the accompanying drawing, wherein- Figure 1 shows the novel lath as applied to an aft sail without a gaff.

Fi 2 is a diagrammatical view taken on line D of Fig. l and showing the position of the lath within the lath pocket, when the sail is slack and when it is acted upon by the wind.

Figs. 3 and 4 are plan views taken on line A of Fig. 1 and showing the lath in the positions corresponding to those shown in Fig. 2.

Figs. 5 and 6 are two embodiments of a lath according to the invention, each view disclosing different means for lengthening the lath.

Referring to the drawing, 1 designates the lath which is preferably of circular cross section as clearly shown in Fig. 2. The curvature of the lath is such that the radius thereof increases gradually from the vertex of the lath toward the ends thereof, if, indeed, it is not preferred to have the extreme parts of the lath wholly straight, which in some cases may be of advantage.

In Fig. 1, the laths are shown to extend from the mast 2 to the after leech 3 and to be inserted in lath pockets 4 affording plenty of room for the lath to move therein in accordance with the bulging of the sail. As shown in Fig. 2, the lath rests at the bottom of the pockett, when the sail is at rest, whereas, when the sail is bulging out the vertex of the lath moves toward the top portion of the pocket. In this way, the lath may assume any intermediate position between the bottom and the top of the pocket, according to the strength of the wind, or the position of the sail.

As will be further seen from Figs. 1 and 3, the lath does not extend exactly to the after leech 3 of the sail, when the latter is slack, there being left some clearance be tween the extreme end 5 of the lath and the leech. However, as the sail is bulging under the pressure of the wind, the extreme end of the lath approaches to the leech 3 of the sail, until eventually (Fig. 4) when the bag of the sail is fully developed, the end of the lath and the leech 3 will meet. The after leech of the sail then has the position indicated by the dotted line 3 To provide for suitable abutments for the ends of the lath,

there. are attached to the foreand after leeches of the sail dished members 6 receiving the rounded ends of the lath.

It may be desirable to let the bag of the sail be more or less pronounced for differ ent wind conditions. According to the present invention the bulging of the sail. may be changed by varying the length of the laths, while the abutments are fixed and to this end the laths are made adjustable in length. In Fig. 5, the extreme end of the lath is provided with a cap 7 threaded thereon and adapted to be screwed onto the lath, more or less, whereby the active length of the lath may be changed. Instead of threading the cap on the lath, the two members 1 and 7 may be provided with holes 8 (Fig. 6) adapted to register so as to facilitate the insertion of a cotter therethrough.

To prevent wear of the sail, there may be inserted a protecting sheath between the lath and the pocket, such sheath being made of any suitable material which is readily pliable so as not to prevent the rotary movements of the lath. Preferably, this sheath may consist of a wire coil surrounding the lath and attached to the sail.

As according to the present invention, a lath may be made much thicker and stronger than before, it may also be made much longer than heretofore, this being of very great advantage in securing the proper form of the sail, particularly of the upper portion thereof.

What I claim as new and desire to secure by Letters Patent of the United States is 1. In a boat sail, the provision of laths adapted to assume different angular positions relatively to a plane through the ends of the lath and the after leech of the sail or the mast.

2. A boat sail having laths curved in the plane of the sail when the latter is slack.

3. In a boat sail the provision of laths having a curvature directed downwardly in the plane of the sail when the latter is slack said lath being adapted to be angularly displaced with respect to the main plan-e of the sail, around an axis extending through the extreme ends of the lath.

4. r lath having a curvature directed downwardly in the plane of the sail when the latter is slack the curvature of the lath being such that the radius of curvature increases toward the ends of the lath counted from the vertex thereof.

5. A lath as claimed in the preceding claim and extending from the after leech unto the fore leech of the sail.

6. A lath having a curvature directed downwardly in the plane of the sail, when the latter is slack, the curvature of the lath being such that the radius of curvature increases toward the endsof the lath counted from the vertex thereof, such lath extendingfrom the after leech unto the fore leech of the sail and the vertex of the lath being located nearer to the fore leech than to the after leech'of the sail. p

7. A lath as claimed in the preceding claim and having a circular cross section.

8. A lath as claimed in claim 4:, the same being provided witha protecting sheath of some pliable material, surrounding the lath, so as to prevent undue wear of the sail, which sheath is inserted in a pocket provided in the sail and attached to the latter, the said pocket affording plenty of room for the lath to move freely therein.

9. A lath as claimed in claim 4 and combined with two dished members serving as abutments or pivots for the lath.

10. A lath as claimed in claim 4 and adapted to be lengthened or shortened by means of a cap member which is placed on one end of the lath.

In testimony whereof I afiix my signature in presence of two witnesses.

FREDRIK .LJUNGSTROM.

Witnesses:

P. H. BEIGROTH, Inez 'SWENSSOM. 

